Strangely, the following German mistranslations - found through all MC versions I've used so far - were never discovered or corrected to date:
(N.B. -- as no dedicated subforum for language related issues seems to exist, let me suggest to create one! ;-)
1. Under "Options > General" the item "Interface" was mistranslated as "Schnittstelle"; the correct German word to use here is "Oberfläche". (A common mistake since the English word denotes two very different things in German, one is visible to humans, the other to machines only... ;-)
2. Under "Options" the topmost navigation item "Audio" is mistranslated as "Musik"; the correct German word here would be "Wiedergabe" (or "Audio" as well), because the page has many general playback settings pertaining to video as well (but are not listed there, eg. "Title change, Cue, Skip, Stop" etc).
The best solution though -- move all these and other related setting to a new "Playback" (= German "Wiedergabe") navigation item in the Options window!
3. When connecting to another MC library server (in client mode), the status message word "access key" was mistranslated as "Zugriffstaste"; the correct word here is "Zugriffsschlüssel" (refering to the default string "Pajsrv" being checked for access, not a keyboard button as the translation suggests ;-).
Please consider this a free contribution by a regular MC user! (If you at JRiver are interested though, feel free to contact me for regular translation and/or proofing services. Being a professional English / German linguist, translator & editor, I have plenty of experience in software localization! ;-)
Best regards,
A.